Arc lamps or mercury vapor lamps, simple or doped, are generally fed by alternating current through a choke or ballast which limits the intensity of the current.
It is known that these lamps have a very high luminous output, much greater than incandescent lamps. However, projectors of self-contained small exploration vessels for underwater work which are fed by electrical energy by a group of batteries continue to be provided with incandescent lamps. Since these lamps are relatively powerful, for example, 400 watts, there is a rapid discharge of the batteries which limits the range of these vessels.